Horton

Re: Pluggable Storage - Andres's take

Andres Freund <andres@anarazel.de>

View thread View on postgr.es
From: Andres Freund <andres@anarazel.de>
To: Ashwin Agrawal <aagrawal@pivotal.io>
Cc: Heikki Linnakangas <hlinnaka@iki.fi>, Haribabu Kommi <kommi.haribabu@gmail.com>, Asim R P <apraveen@pivotal.io>, Pg Hackers <pgsql-hackers@postgresql.org>, Dmitry Dolgov <9erthalion6@gmail.com>, Alvaro Herrera <alvherre@2ndquadrant.com>, Alexander Korotkov <a.korotkov@postgrespro.ru>
Date: 2019-03-06T02:34:03Z
Lists: pgsql-hackers 
Hi,

Thanks for looking!

On 2019-03-05 18:27:45 -0800, Ashwin Agrawal wrote:
> While playing with the tableam, usage of which starts with commit
> v12-0023-tableam-Introduce-and-use-begin-endscan-and-do-i.patch, should we
> check for NULL function pointer before actually calling the same and ERROR
> out instead as NOT_SUPPORTED or something on those lines.

Scans seem like absolutely required part of the functionality, so I
don't think there's much point in that. It'd just bloat code and
runtime.


> Understand its kind of think which should get caught during development.
> But still currently it segfaults if missing to define some AM function,

The segfault iself doesn't bother me at all, it's just a NULL pointer
dereference. If we were to put Asserts somewhere it'd crash very
similarly. I think you have a point in that:

> might be easier for iterative development to error instead in common place.

Would make it a tiny bit easier to implement a new AM.  We could
probably add a few asserts to GetTableAmRoutine(), to check that
required functions are implemted.  Don't think that'd make a meaningful
difference for something like the scan functions, but it'd probably make
it easier to forward port AMs to the next release - I'm pretty sure
we're going to add required callbacks in the next few releases.

Greetings,

Andres Freund

Commits

  1. Add default_table_access_method to postgresql.conf.sample.

  2. tableam: Avoid relying on relation size to determine validity of tids.

  3. tableam: Don't assume that every AM uses md.c style storage.

  4. Allow pg_class xid & multixid horizons to not be set.

  5. Fix slot type issue for fuzzy distance index scan over out-of-core table AM.

  6. tableam: comment and formatting fixes.

  7. table: docs: fix typos and grammar.

  8. tableam: basic documentation.

  9. Only allow heap in a number of contrib modules.

  10. tableam: Add table_finish_bulk_insert().

  11. tableam: sample scan.

  12. tableam: bitmap table scan.

  13. tableam: Move heap specific logic from estimate_rel_size below tableam.

  14. tableam: VACUUM and ANALYZE support.

  15. tableam: relation creation, VACUUM FULL/CLUSTER, SET TABLESPACE.

  16. tableam: Support for an index build's initial table scan(s).

  17. tableam: Add table_get_latest_tid, to wrap heap_get_latest_tid.

  18. tableam: Add helper for indexes to check if a corresponding table tuples exist.

  19. tableam: Add and use table_fetch_row_version().

  20. tableam: Use in CREATE TABLE AS and CREATE MATERIALIZED VIEW.

  21. Ensure sufficient alignment for ParallelTableScanDescData in BTShared.

  22. Don't reuse slots between root and partition in ON CONFLICT ... UPDATE.

  23. Use a virtual rather than a heap slot in two places where that suffices.

  24. Store tuples for EvalPlanQual in slots, rather than as HeapTuples.

  25. Use slots in trigger infrastructure, except for the actual invocation.

  26. Store table oid and tuple's tid in tuple slots directly.

  27. Allow to use HeapTupleData embedded in [Buffer]HeapTupleTableSlot.

  28. Add ExecStorePinnedBufferHeapTuple.

  29. Add ArchiveOpts to pass options to ArchiveEntry

  30. Rename RelationData.rd_amroutine to rd_indam.

  31. Rephrase references to "time qualification".

  32. Move remaining code from tqual.[ch] to heapam.h / heapam_visibility.c.

  33. Move generic snapshot related code from tqual.h to snapmgr.h.

  34. Remove superfluous tqual.h includes.

  35. Don't duplicate parallel seqscan shmem sizing logic in nbtree.

  36. Move vacuumlazy.c into access/heap.

  37. Support parallel bitmap heap scans.